The present invention relates generally to electronic security systems for the protection of property against fire and theft, and, more particularly, to security systems of the type which includes a central controller or monitoring station connected with a number of remote stations at different locations.
Sophisticated equipment for monitoring burglar and fire alarms is relatively expensive, usually too expensive for most owners of small and medium-sized businesses. Consequently, many people prefer to use systems in which a central monitoring facility is capable of monitoring a large number of protected premises. There already exist various systems having a central computer or controller for polling a number of remote transponders connected to the controller by telephone lines, but these prior systems typically have the capability of interrogating only a single alarm condition at each transponder site. More complex systems allowing the monitoring, over telephone lines, of multiple alarm conditions at multiple sites are, of course, well within the state-of-the-art of today's digital communication technology, but a key limiting factor is cost, especially cost of the modem equipment. Complex systems having multi-wire connections to a central site are also available, but again, cost may be a limiting factor.
As mentioned already, the cost of security equipment is, to many buyers, critical. If the cost of a transponder unit having the desired capabilities exceeds the incremental cost of insurance that would be required to cover the premises without installation of the transponder, then the security equipment has little or no commercial value.
It will be appreciated from the foregoing that there is a definite need in the security alarm industry for a security polling system utilizing transponders which are economical to manufacture, but which also have the capability of monitoring and transmitting multiple alarm conditions, and of performing other functions usually only found in expensive multi-wire systems. The present invention satisfies this need.